I agree with SarahW: spend some time reading here and then come back with more specific questions. It's really difficult to answer such open-ended questions, especially about costs since everyone's RVing style is different.
For example, are you going to travel every day, or are you going to stay in one place for a week, a month? Length of stay not only impacts fuel costs, but also RV park costs.
Are you going to stay exclusively at high end RV parks, or are you going to dry camp/boondock for free?
Are you going to eat out every single meal, or are you going to prepare all your meals in the RV?
Are you going to be eating steak and lobster or rice and beans?
Even with a trailer (travel trailer or fifth wheel?), the initial cost will depend greatly on whether you buy new or used and whether or not you buy a vacation unit, or a high end unit suitable for fulltiming.
All of these types of decisions will depend on how much it will cost YOU to travel in your RV.
2014 Winnebago Aspect 27K
2011 Kia Soul